WAUWATOSA, Wis. – Officers detained a black teenager riding in a car with his white grandmother over the Labor Day weekend after police say they got a report of a robbery in progress.

Wauwatosa police called it a misunderstanding, but the family's attorney, Joy Bertrand, said the young man's rights were violated.

During a traffic stop around noon on Sept. 2 near Burleigh Street and Mayfair Road, dash cam video shows Wauwatosa police officers place the 18-year-old man in handcuffs, and sit him down in the back seat of a squad car.

At one point, an officer also pulls his gun from the holster and points it toward the ground before approaching the car.

However, the supposed robbery victims were the teen's grandmother and her female friend, according to the Journal Sentinel.

"I'm sure he (the person who reported it) saw two white ladies in a car with a black kid and he made some assumptions," the grandmother can be heard saying.

After police learned the woman was the young man's grandmother, on her way back from church to drop him off at work, they explained why he was detained.

"Some guy comes up to me in a car and says that guy (her grandson) is robbing you," an officer said in the video.

"I'm guessing what this sounds like is a really big misunderstanding," another officer said.

Bertrand said the video indicates that officers violated the 18-year-old's "right to be free from an unreasonable stop, the right to be free from an unreasonable seizure."

Police said the following in a statement posted to Facebook:

A Wauwatosa Police Officer was on patrol on Sunday 9/2/18 at approximately 11:49 a.m. and was flagged down by an African American male and African American female who indicated a robbery either was occurring or had just occurred and the suspect was a black male in the back seat of a blue Lexus.

Bertrand said she also wants proof of the initial robbery report, and that police had reasonable suspicion to follow up.

"So now, just crazy people can come up to a police car and say, 'that car's being robbed?'" said Bertrand.

In a statement, Wauwatosa Police Department officials said, in part, that they "acted professionally during the entire interaction."

The department added:

"The 18 year old male was detained based on reasonable suspicious of approximately 6 minutes while officers investigated. the 18 year old and other occupants were then allowed to leave. The original citizen who reported this to police did not stay in the area, as requested by officers, and has yet to be located to get a formal statement."

The family's attorney said once she has more of the facts, she will comment on any next steps.